This invention is generally directed to a device or mechanism for assisting in the lifting of large enclosures. More specifically, this invention is directed to a device or mechanism for assisting in the lifting of a tall hood member that provides above-ground entry into the mechanical section of a buried pumping station.
It has hereto been common practice to use gas shocks to assist in the opening or lifting of large or tall enclosures. This was typically accomplished using one of two methods. In the first method, the gas shocks were under-sized to allow the user to still be able to close the enclosure, while still providing a degree of assistance. In the second method, the travel of the enclosure is limited to forty five degrees. This permits the gas shocks to be sized correctly, but prevents the enclosure from being fully opened unless the gas shocks are uninstalled. Both of these options require the use of an end restraint to prevent the hood from over-extending the gas shock and thereby shortening its life.
The design of assist mechanisms that utilize gas shocks for enclosures that are tall presents unique problems. While the gas shocks will successfully lift the enclosure, in the full open position (approximately ninety degrees from horizontal), the center of gravity is located behind the hinge. As a consequence thereof, in order to close the enclosure, the operator is required to not only overcome the weight of the enclosure, but also the strength of the gas shocks. This in turn limits the strength of the shock that can be used, as a stronger shock would severely hamper an operator""s ability to close the enclosure. Since the strength of the gas shock is limited, the amount of assistance that can be supplied in opening the enclosure is also limited.
The alternative is to limit the travel of the enclosure such that the gas shocks do not push the center of gravity of the enclosure past the hinge. In some applications, this only allows for the enclosure to be opened about forty five degrees instead of ninety degrees. Some applications have allowed the gas shocks to be removed as a part of operating the enclosure when it is necessary to open it beyond the travel of the gas shocks.
Additionally, it has heretofore been necessary to take great care to prevent the gas shocks from over-extending, such as the utilization of an end-stop. If the gas shocks are permitted to fully extend before the endstop is engaged, the weight of the enclosure will tend to over-extend the shocks and thereby greatly reduce their useful life.
In accordance with the present invention, a left assist mechanism is provided that decreases the work required by an operator to fully open an enclosure or hood for entry into a mechanical section of a system, such as a wastewater or sewage pumping station.
The lift assist mechanism includes a swing arm member and an expandable strut or gas shock member. The swing arm member has a first end portion pivotally attached to the body member and a second end portion pivotally attached to a first end portion of the strut member. The strut member has a second end portion that is pivotally attached to the enclosure member.
The body member has a base plate member associated therewith. The strut member has a contracted condition when the enclosure member is in its closed portion and an extended condition when the enclosure member is in its intermediate and fully open position. The pivot point between the swing arm member and the first end of the enclosure member is pressed against the base plate when the enclosure member is in its closed and intermediate positions. The pivot point between the swing arm member and the first end of the enclosure member is lifted up from the base plate member when the enclosure member is in its open position.